Mechanical stretch of human tissue has been known to enhance collagen build up both in vitro, relating to pulmonary artery fibroblasts (Jia Liu et al. Mechanical stretching stimulates collagen synthesis via down-regulating SO2/AAT1 pathway. Sci. Rep. 6, 21112; doi: 10.1038/Srep 21112 (2016) and in vitro (see below). Stretching has been shown to regulate cellular proliferation in human epidermal keratinocytes (Soichiro Yano et al. “Mechanical stretching in vitro regulates signal transduction pathways and cellular proliferation in human epidermal keratinocytes.” J. Invest. Dermatol. 122: 783-790, 2004. Further, in another research stretching has been demonstrated to affect epidermal thickness and develop the basement membrane in human skin equivalents in vitro. (Eijiro Tokuyama et al. Mechanical stretch on human skin equivalents increases the epidermal thickness and develops the basement membrane. Plos one DOI:10: 1371, 2015.
Another aspect of skin relating to personal care, cosmetics and medicine, is the hindrance which the outer layer of the skin presents to permeation of medicinal an conditioning agents. In this respect Trommer H and Neubert R. H. H. (“Overcoming the stratum corneum: the modulation of skin penetration”, Skin pharmacol. physiol, 2005; 19:105-121. Chemical and physical methods of enhancing the penetration through the stratum corneum are discussed.
Wrinkles in the complexion skin and other places are a subject of numerous efforts aiming to evade or mitigate the phenomenon. For example J. L. Contet-Audonneau et al. in “A histological study of human wrinkle structure: comparison between sun—exposed areas of the face, with or without wrinkles and sun—protected areas” (Br. J. of Dermatol. 1999: 140: 1038-1047